9mm Mike, the top tang safety is not a myth. You might be able to easily and quickly use the dreaded crossbolt safety, but that would be in spite of its location, not because of it.
The thumb is wider, stronger, and more independent of the other digits on the hand, making it the natural choice for safety duty.
The top tang safety can be cleared with a sweeping motion, whereas the crossbolt safety must be searched out (find the triggerguard, and go forwards or backwards from there.)
I will be the first to admit that I might be prejudiced because I am a lefty, and suffered the ignomity of having to hook my finger over and around the trigger guard on righthanded guns. But even on guns where the crossbolt can be reversed, (My Model 12) these type safeties always felt clumsy. I just feel that trigger fingers are for triggers, and the thumb is for the safety, and I will never forgive Ruger for screwing up their Model 77 rifle with that ridiculous wing safety, but that is for the rifle section.